A conventional multilayer module is described with reference to the drawings.
FIG. 12 shows a cross sectional view of a conventional multilayer module. Referring to FIG. 12, circuit board 300 is a multilayer substrate, conductor pattern 400 is provided on upper surface 300a of circuit board 300, electronic component 200a such as a semiconductor device chip, chip component, etc. is mounted on conductor pattern 400. At bottom surface 300b of circuit board 300, conductor pattern 500 is provided.
Resin layer 600 is provided on upper surface 300a of circuit board 300, in a manner to cover the outer surface of electronic component 200a. Conductor pattern 700 is provided on upper surface 600a of resin layer 600. Conductor pattern 700a disposed on upper surface 600a of resin layer 600 and conductor pattern 500a disposed at bottom surface 300b of circuit board 300 are connected by means of through hole 800 which is penetrating both circuit board 300 and resin layer 600.
In addition, a semiconductor device chip, a chip component or the like electronic components 200b are mounted on conductor pattern 700. Resin layer 900 is provided on upper surface 600a of resin layer 600 covering electronic component 200b. Conductor pattern 1000 is provided on upper surface 900a of resin layer 900. In order to connect conductor pattern 1000a formed at upper surface 900a of resin layer 900 with conductor pattern 700b formed at upper surface 600a of resin layer 600, through hole 1300 is provided penetrating both resin layer 600 and resin layer 900. Through hole 1300 is connected also with conductor pattern 500b at the bottom surface 300b side of circuit board 300.
Multilayer module 120 thus constituted is further provided with conductor patterns 500c and 1000b on bottom surface 300b of circuit board 300 and upper surface 900a of resin layer 900, respectively, at the neighborhood of an outer circumference. These conductor patterns 500c and 1000b are connected by means of through hole 1300 formed at the side wall of multilayer module 1200. Conductor pattern 500c and through hole 1300 are used as the connection terminal for mounting multilayer module 1200 on a mother board.
Now a method of manufacturing the above-configured conventional multilayer module is described with reference to the drawings.
FIG. 13 is a manufacturing flow chart of a conventional multilayer module.
At parts mounting step S21a in FIG. 13, semi-finished electronic component, chip component 200a is mounted on upper surface 300a of circuit board 300, which circuit board being introduced to the work stage for a plurality in the connected state. At resin layer forming step S22a, resin is supplied on upper surface 300a of circuit board 300 to cover semi-finished electronic component, chip component 200a which was mounted at step S21a. The resin is heated and cured. After resin layer 600 is formed at step S22a, a copper foil is bonded on upper surface 600a of resin layer 600, at conductor layer forming step S23a. 
At terminal and pattern forming step S24a, the conductive foil is formed into a certain specified pattern 700, 700a by etching or the like process. Through hole 800 is also provided for connection between conductor patterns 700a and 500a. This completes a first layer of multilayer module 1200.
For the second and subsequent layers, those steps from parts mounting step S21b up to terminal and pattern forming step S24b are repeated, like in the first layer making, for a number of resin layers stacked. After internal connections are completed at terminal and pattern forming step S24b making it a finished multilayer module 1200, circuit board 300 and resin layers 600, 900 are cut altogether into individual pieces at separating step S25.
Prior arts related to the present invention are disclosed in, for example, Japanese Patent Unexamined Publication No. 2000-183283, Japanese Patent Unexamined Publication No. 2003-31954.
In an above-configured conventional multilayer module, however, through hole 1300 for connecting conductor pattern 1000a with conductor pattern 700b is formed after resin layer 600 and resin layer 900 are stacked one after the other on circuit board 300. As a result, the through hole penetrates both of resin layers 600 and 900. Therefore, semi-finished electronic component, chip component 200a can not be disposed in a place where there is through hole 1300. This means that the area in which no electronic component can be mounted due to a through hole further increases along with the increasing number of stacked resin layers. Furthermore, since through hole 800 is penetrating resin layer 600 through, no semi-finished electronic component, chip component 200a can be mounted on the area of through hole.
As described in the above, the non-mountable area for electronic component in a conventional multilayer module is caused by through holes 800, 1300 provided for interlayer connections. A problem with the conventional configuration is that it makes multilayer modules larger in size.